The historic 2022 flood in Yellowstone National Park washed out roads. Flooding in Soda Butte Creek caused significant damage to several sections of road along the Northeast Corridor between Cooke City, Montana, and Tower Junction. The Northeast Entrance Road opened on October 15, 2022, after repair work was completed to this and other flood-damaged sections. Image credit: NPS
In the aftermath of the devastating 2022 Yellowstone floods, we examined historical river flows. Could our insights help predict future events?
By Ally Marrs, Teodora Rautu, David Thoma, Ann Rodman, Mike Tercek, and Andrew Ray
In June 2022, rivers in Yellowstone’s Northern Range exceeded century-long flood records. The flooding caused widespread damage and disrupted park operations, forcing the park to temporarily close to visitors. In the wake of the flood, many were left wondering what caused this natural disaster, if it could happen again, and whether there was a way to know what was coming ahead of time. We analyzed the historical flow record and worked on modeling the conditions that led to the disaster. Our findings can help alert scientists and land managers about future floods.
Map of Northern Yellowstone National Park showing major river systems, locations of flood damaged infrastructure (red and orange dots), and U.S. Geological Survey and other hydrologic gaging stations (blue boxes). Major damage (red dots) refers to structural damage or other significant damage that required extensive repairs. Minor damage (orange dots) refers to repairable or non-structural damage to infrastructure. Image credit: NPS
In the aftermath of this flood, we examined past flow records to better understand its magnitude in the context of history. For three of the Northern Range rivers (the Gardner, Lamar, and Yellowstone), we have about one hundred years of flow data collected at permanent U.S. Geological Survey streamflow gauging stations. Historical data provide insight on short- and long-term flow variation in free-flowing rivers like these. We gained context for the 2022 flood by comparing it to previous flow records.
We found that the Yellowstone River 2022 flood exceeded all previous floods at the Corwin Springs gauge since 1890. The volumetric flow rate measured by the gauge was 50 percent greater than the previous record, which translates to 17,000 cubic feet per second higher. The June 2022 floods were referred to as a “500-year flow event.” But this doesn’t mean a flood of this size couldn’t happen again sooner, particularly since precipitation extremes are becoming more frequent. It means that there is a 1-in-500 chance of a flood of this size happening in any given year.
We analyzed trends in high flows over time and found that flows in the 95th percentile—those that are greater than 95 percent of daily flows—have been increasing in size. This means that a 95th percentile flow in 2022 was larger than a 95th percentile flow in 1922. Not only is the amount of water flowing through these rivers changing, but also the timing of high flows. The peak flow date—the day of the year when the highest flow occurs—has been getting earlier over time for all three major Northern Range rivers. There are year-to-year variations, but on average, peak flow is occurring one day earlier every 11 years.